1. Field of the Invention
The invention relates primarily to shims used in construction projects. More specifically, the present invention is directed to a shim and method of using a shim that can easily be placed within a gap.
2. Description of the Related Art
In building construction, walls are commonly constructed with rough openings, which are provided for the subsequent installation of doors, windows, or a variety of other construction items. The walls are most commonly constructed from either wood, cement block, or poured concrete, with most commercial or community-living construction projects utilizing poured concrete. The materials used for walls in residential construction may vary based on geographic location, but are most often wooden frame, cement block, or a combination of both.
Doors and windows intended to fill the rough openings are often pre-manufactured at the factory to meet the specifications of the builder. To allow for installation of the doors and windows, the builder must make the openings in the building slightly larger than the object that is to be inserted into the particular opening. Due to tolerances in materials, human error, and other factors, the walls of the rough openings may not be true and the intersections of the walls often do not meet at perfect 90-degree angles. These unpredictable variances add to the difficulty of installing the pre-manufactured doors and windows.
The installation of a door or window is as follows: The frame is inserted into the rough opening in a particular wall. Because the frames are slightly smaller than the rough opening, relatively small gaps exist between the outside surfaces of the frame and the corresponding inside surfaces of the walls of the rough opening. The direction “inside” refers to a direction toward a center region of the rough opening. Similarly, the direction outside refers to a direction opposite the center region. To fill the gaps between the frame and the opening, material is placed between the frame and the corresponding inside surface of the opening. The material placed in the gaps is referred to as a “shim,” and is utilized to bridge the gap between the wall and the frame and bring the two into physical communication with each other. Different amounts of shim material are used at various shim points around the frame to account for dimensional variances in the rough opening in the wall. The result is a frame that is physically supported and level. The frame is then secured to the wall using common nails, screws, bolts, or other similar methods of attachment. Although several attachment methods are suitable, the use of screws will be referred to hereafter.
If the shims are placed more than a few inches away from a point where the installation screw attaches the frame to the opening in the wall, the pressure exerted by the head of the screw on the relatively thin frame material, usually aluminum, as the screw is turned, will flex and distort the frame. It is therefore desirable to place the shims, among other places along the frame, as close as possible to the screws. One method, as is done in the prior art, is to provide a U-shaped shim that will slide around and contain the screw within its channel. This provides a solid base between the inside surface of the wall of the rough opening and the outer surface of the frame. As a result, the frame will not distort under normal pressure when the screw is tightened.
The size of the gap between the frame and the rough opening may vary along the length of the opening. It is therefore desirable to have a shim that varies in thickness, or a plurality of shims that can be stacked to achieve the particular desired thickness.
Several prior art shims exist that have the above-mentioned features. For example, U.S. Pat. No. 6,560,934 to Workman, describes a horseshoe-shaped shim that can fit around a screw or bolt and also has the feature of being snappably connectible to adjacent shims through upwardly extending projections on a surface of a first shim and corresponding recessed areas on a second shim. Workman however, has several disadvantages. When installed between two vertical elements, the Workman shim must be installed around an installation screw or bolt and be aligned so that the open end of its horseshoe shape faces in a downward direction. Otherwise, the shim will not stay in its intended position and will fall off of the installation screw or bolt. The shims may also rotate with the screw during the tightening step and can slip or dislocate. Secondly, the Workman shims are difficult to install around the installation screws or bolts because they are concealed behind the frame and are not provided with an easy way to insert them between the rough opening and the frame once the frame is in place. Finally, the Workman shims are not suitable for placement between two vertical elements not having a screw or bolt to support them, because they will dislocate without a structure to hold them in place.
U.S. Pat. No. 6,159,575 to Rathsack discloses a shim having arms defining an insert slot with an inner edge formed with an outwardly directed bevel forming an insert aid. The bevels help grip the installation screw and allow the shim to stay in place while the screw is tightened and the shim is compressed between the frame and the rough opening. Additionally, the bevels allow the shim to be installed in any orientation, with regard to the open end of the shim, without later becoming dislocated. However, the bevels only allow the shims to hold their position when the shims are installed around a screw, bolt, or other similar mounting structure. It is often necessary however, to insert a shim that will maintain its position between structures forming a gap that does not contain a screw, bolt, or other similar mounting structure. The bevels on the Rathsack shim will not be useful in this location. The Rathsack shim also suffers from the same deficiency as does the Workman shim. When placed within a gap defined by two vertically oriented elements, without a mounting structure, the shim will have a tendency to fall and dislocate. Additionally, neither the Rathsack nor Workman shims provide an attachment that allows the shim to easily be inserted completely within the gap.
A shim produced by Grove Products, Inc. and described in their 2003 catalog, found at http://www.groveproductsinc.com/shim_stacks.htm, and a similar shim described in the Sommer & Maca Industries, Inc. 2002-2003 catalog, found at http://www.somaca.com/Product Detail.asp?ProductNumber=345-5025, disclose respective plastic and a PVC shims having a general horseshoe shape with two arms defining an insert slot. At the portion of the shim opposite the extending arms is a rectangular tab. The tab is provided as a method for completely inserting the shim between a gap where the installer's fingers may not fit. In the Sommer & Maca shim, the tabs are provided at their base, which is the connecting junction to the main body of the shim, with a decreased thickness of the material. This decreased area allows the tab to easily snap off of, and away from, the body of the shim once the shim is fully inserted between the gap. Additionally, both publications disclose a shim that has multiple perforations at locations along the arms, which span the width of the arms in a direction perpendicular to the insert slot defined by the arms. The perforations allow the length of the arms to be reduced by simply applying a bending pressure to the arm near one of the perforation points, which will cause a section of the arm to break away from the body of the shim.
The published shim designs also disclose shims that are provided in attached stacks of multiple shim elements. The stacks may be snapped apart to achieve the desired thickness of the gap to be filled with the shim.
Neither the Sommer & Maca, Grove Products, nor any of the shim designs described above, provide a shim that can easily be placed within a gap, is self-tensioning between the gap, and will hold its inserted position without reliance on supporting structure other than the elements defining the gap itself.